So Ginsberg and her colleagues devised a measurement that transforms an optical “super-resolution” microscopy known as STED (stimulated emission depletion) into a tracker of excitons on these short scales in an organic semiconductor. The technique makes it possible, for the first time, to relate the characteristics of exciton migration efficiency to nanoscale structures within light harvesting materials. “We ended up using the spatial profile of light pulses and the way that they interact with the material in order to excite very small and localized regions that have very sharp boundaries,” she said.